Apparatus and method for cooling an electric motor

ABSTRACT

An improved electric motor cooling construction where the motor stator is contained within the motor housing. The motor covers and motor housing are designed to provide direct increased airflow to the motor stator, and coil windings to provide better airflow through the motor resulting in improved cooling.

This application is a Continuation of U.S. application Ser. No.10/234,530 filed on Sep. 3, 2002.

FIELD OF THE INVENTION

This invention relates to cooling of electric motors. More specifically,the present invention relates to an apparatus and method to improve thecooling of electric motors by creating a more even airflow over themotor coil windings and stator laminations.

BACKGROUND OF THE INVENTION

The majority of all commercial and industrial electric fans have anelectric motor. These motors generate heat from the motor windings. Thisheat, when excessive, can degrade overall performance and longevity ofthe motor. Typically fan designers try to use the “suction” on the rearof the blade and blade hub to help pull the air through the rear of themotor towards the front. This airflow is important in providing coolingfor the motor windings, however, there are many structurally necessaryelements that are part of the motors which limit the amount of airflowthat can help cool the motor.

One of these structurally necessary elements is the motor housing. Themotor housing is used to mount the bearings, which support the shaft forrotation. The housing also protects the windings from damage after themotor is assembled, and also acts as an enclosure. The housing hasopenings, the size of which is mandated by standards organizations suchas Underwriters Laboratories. If the openings in the housings exceed acertain mandated size, special cover materials or additional enclosuresare required. Motors housings can be cast aluminum, zinc or stampedmetal. Motor housings are in contact with the stator, and, in the priorart, closely surround the windings/coils, which leaves little to no areafor “air flow” through the motor.

A second structural element, which limits airflow through the motor,consists of the stator and rotor. The stator consists of a stack ofsteel laminations which have copper magnet wire wound on them.Conventionally, the steel is normally sandwiched between the front andthe rear housings.

Looking through the rear housing, the wire and stator laminations blockthe airflow through the motor. The area of opening for air movementthrough the stator is generally quite small even in relationship to themandated holes in the motor housings and the motor covers. The prior arthousings are so tight against the outside of the laminations that theygenerally do not allow adequate airflow through the housings and by thecoils. The two motor housings typically have a gap where the statorsits, which also allows some of the air entering the rear motor housingto escape, thereby completely bypassing the front coil.

A third structural element, which effects airflow through the motor, isthe outside motor cover. For safety purposes most electric motors aresurrounded by “motor covers.” Common materials for motor covers aremetal and plastic. These covers are usually aesthetic and cover anyelectrical materials and/or hot motor surfaces. These, motor covers mayadditionally impede airflow through the motor. Motor covers have ventstructures which are usually located at the rear and the front of themotor. Venting provides an airflow path that will enter the “rear motorcover” and flow mostly around the outside of the motor housing drawingheat from the housings, which in turn draws heat from thestator/windings. This prior art airflow path 30, as illustrated in FIG.2, has little to no effect on the front coil area of the motor,resulting in uneven heat dissipation throughout the windings.Accordingly, the prior art airflow pattern enters the rear motor cover11 and travels mainly between the inside of the motor cover walls andthe outside of the motor housings 14 and 15. This prior art constructionand its resultant airflow does not provide adequate and even cooling ofthe motor.

The inventive design, set forth in detail below, forces a greater amountof air to be drawn into the motor housing and flow in a path thatcontacts both the front and rear windings and provides more even coolingof both the front and rear windings and the stator.

SUMMARY OF THE INVENTION

In view of the shortcomings of the prior art, the present inventionprovides a method and apparatus for improved electric motor cooling.

It has now been found that an improved electric motor coolingconstruction is available wherein the motor housing and covers draw inmore air and channel it into an air path that directly contacts themotor stator and coil windings to remove the heat and to more evenlycool the motor.

The improved electric motor comprises a first housing having a firstwall defining a first interior space, and at least one opening disposedon a surface of the first housing; a second housing having a second walldefining a second interior space, and at least one opening disposed on asurface of the second housing; and a stator having a plurality oflaminations a first portion of windings and a second portion ofwindings, the plurality of laminations disposed substantially within thefirst interior space and the second interior space, such that air flowsi) into the at least one opening in the first housing, ii) over thefirst portion of windings, substantially all an exterior portion of thestator laminations, and the second portion of windings, and iii) out theat least one opening in the second housing.

According to another aspect of the invention, a front cover havingopenings is coupled to the surface of the second housing, and a rearcover having openings is coupled to the front cover and substantiallysurrounds the first and second housings. The openings in the rear coverare in fluid communication with the openings in first housing, and theopenings in the front cover are adjacent and in fluid communication withthe openings in the second housing.

According to a further aspect of the invention, the stator issubstantially square.

According to yet a further aspect of the invention, the at least oneopening in the first housing is a first plurality of openings and the atleast one opening in the second housing is a second plurality ofopenings, at least a portion of the first plurality of openings and atleast a portion of the second plurality of openings in respective planessubstantially parallel to one another.

According to another aspect of the invention, the motor housings are incontact with the stator and have airflow channels therebetween.

According to yet another aspect of the invention, the stator issubstantially round.

According to still another aspect of the invention, the front motorcover contacts the front motor housing to seal off airflow, forcing airthrough the motor.

According to yet a further aspect of the invention, the front and rearmotor housings have a reduced gap therebetween so that airflow isinhibited from escaping from between the motor housings.

According to another aspect of the invention, the electric motor has areduced operating temperature and a more even cooling of the statorwindings and laminations.

These and other aspects of the invention are set forth below withreference to the drawings and the description of exemplary embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following Figures:

FIG. 1 is an exploded perspective view of a prior art electric motorassembly;

FIG. 2 is a sectional view of the prior art motor assembly of FIG. 1;

FIG. 3A is a perspective view of an electric motor incorporating a firstexemplary embodiment of the present invention;

FIG. 3B is a perspective view of an electric motor incorporating asecond exemplary embodiment of the present invention;

FIGS. 3C and 3D are sectional views illustrating details of theexemplary embodiment of FIG. 3B;

FIG. 4 is a sectional view of the motor of FIGS. 3A and 3B;

FIG. 5 is a chart showing the performance characteristics of a prior artelectric motor;

FIG. 6 is a chart showing the performance characteristics of an electricmotor which incorporates an exemplary embodiment of the presentinvention, and;

FIG. 7 is an illustration of an oscillating fan incorporating anexemplary embodiment of the present invention.

It should, of course, be understood that the description and drawingsherein are merely illustrative and that various modifications andchanges can be made in the structures disclosed without departing fromthe spirit of the invention. Like numerals refer to like partsthroughout the several views.

DETAILED DESCRIPTION

The entire disclosure of U.S. patent application No. 10/234,530 filed onSep. 3, 2002 is expressly incorporated by reference herein.

When referring to the preferred embodiment, certain terminology will beutilized for the sake of clarity. Use of such terminology is intended toencompass not only the described embodiment, but also technicalequivalents which operate and function in substantially the same way tobring about the same result.

Referring now more particularly to the drawings and FIGS. 1 and 2thereof, a prior art electric motor assembly 10 is therein illustrated.

As shown in FIG. 1, motor assembly 10 includes rear cover 11, frontcover 12 of a generally circular configuration, with motor 50 containedtherein.

Motor 50 includes front and rear motor housings 15 and 14, respectively,which are in contact with and are secured to the outside surfaces ofmotor stator 17, in a conventional manner, retaining it therebetween,such as by screws 18 extending into spaced bosses 20, on motor housings14 and 15.

Motor stator 17 is of square configuration and extends outside motorhousings 14 and 15.

Referring now to FIG. 2, motor assembly 10 is also provided with rotor(not shown) and output shaft 22, which has a hub 23 of fan bladeassembly 24 secured thereto in a conventional well known manner. Motorstator 17 includes a plurality of laminated sheets of steel 25, withrear coil windings 26, and front coil windings 27, secured thereto in awell known manner.

Referring again to FIG. 2, the airflow pattern for cooling motor 50 isillustrated by curved lines 30, which show air entering through openings31 in rear cover 11, over a motor capacitor 32, over the exterior ofrear motor housing 14, over the exterior of front motor housing 15 andexiting through openings 35 in front cover 12 (best shown in FIG. 1).

As is clearly shown in FIG. 2, airflow 30 does not directly contact thelaminated sheets 25, and the rear coil windings 26 and the front coilwindings 27 to provide cooling. Rather, airflow 30 ineffectivelyattempts to draw heat away by contacting front motor housing 15 and rearmotor housing 14.

Referring now more particularly to FIGS. 3A and 4, a fan motor assembly300 incorporating a first exemplary embodiment of the present inventionis shown. As shown in FIG. 3A, fan motor assembly 300 includes rearcover 101, rear motor housing 102, front cover 104, and motor 100. Eachof front and rear motor housing 103, 102 have at least one respectiveopening (122 as shown in FIG. 3 a for rear motor housing 102) therein toallow for the passage of air therein (explained in detail below withrespect to FIG. 4). Opening 122 may be formed in a variety of shapes andorientations, such as slots formed circumferencially and/or radially, orcircular openings, for example.

Motor 100 includes rear motor housing 102 and front motor housing 103defining interior spaces 132 and 133, respectively. The front and rearmotor housings 103 and 102 are fastened together by fasteners 105, suchas screws, which may extend through bosses 106 in rear motor housing 102into bosses 107 in front motor housing 103, securing the motor housingsin fluid tight relation with one another. Motor housings 102 and 103 arepreferably of cast or stamped metal such as aluminum, zinc or steel.Alternatively, either or both motor housings 102, 103 may be formed froma polymer, if desired.

Rear cover 101 is secured to the rear motor housing 102 by a fastener108 (best shown in FIG. 4), such as a screw, engaged in boss 109 whichis in turn coupled to housing 102. Front and rear motor covers 104 and101 are preferably of metal or plastic.

Referring now to FIG. 4, motor stator 110 is provided, of a generallysquare configuration, with a plurality of laminated sheets of steel 111,with rear coil windings 112, and front coil windings 114 secured theretoin a well known manner. In this exemplary embodiment, motor stator 110is contained substantially within interior spaces 132, 133 of motorhousing 102 and 103, with only corners 127 of stator 110 extendingbeyond the confines of motor housing 102 and 103 (best shown in FIG.3A). Motor 100 has a rotor 113, output shaft 134, and hub 115 of fanblade assembly 116 secured thereto.

Front cover 104 has inside and outside rims 117 and 118, which receiverear cover 101 therebetween, to couple front cover 104 to rear cover 101and form a seal between front cover 104 and rear cover 101. As shown inFIG. 4, front cover 104 is in close contact with the front motor housing103 and is attached thereto in a conventional manner, using screws, forexample (not shown).

Referring now to FIG. 3B, fan motor 200 incorporating a second exemplaryembodiment of the present invention is shown. As shown in FIG. 3B, thesignificant differences between the first and second exemplaryembodiments is the containment of the entirety of stator 210 withininterior 232, 233 of motor housings 202, 203, respectively, formingairflow cavity 234 between the inner walls of motor housings 202, 203and stator 210. This is best illustrated in FIG. 3C. Similar to thefirst exemplary embodiment, the front and rear motor housings 203 and202 are fastened together by fasteners 105, such as screws, which mayextend through bosses 206 in rear motor housing 202 into bosses 207 infront motor housing 203, securing the motor housings in fluid tightrelation with one another.

In one version of this exemplary embodiment, stator 210 is substantiallyround and attached to at least one of housings 202, 203 usingconventional means, such as staking through the walls of either or bothhousings 202, 202, press fit within either or both housings 202, 202, orstops incorporated within interior spaces 132 and 133 of the motorhousings, for example. Alternately, and as shown in FIG. 3D, stator 310may be substantially square.

In an exemplary embodiment of the present invention, motor 100 may be apermanent split capacitor (PSC) motor having any of a variety of poleconfigurations, such as 4 poles and 6 poles. The invention is not solimited, however, and it is contemplated that motor 100 may be of othertypes, such as a shaded pole motor, for example.

As shown in FIG. 4, air, depicted by air flow lines 128, is drawn towardand enters motor 100 by action of fan blade 116, through openings 120 inrear cover 101, and through openings 122 in rear motor housing 102, overand in contact with rear coil windings 112, the exterior portions oflaminated sheets 111, front coil windings 114, exiting through openings125 in front housing 103, and finally out the front cover 104 throughopenings 126, thereby drawing heat out of fan motor 100. This improvedairflow is substantially identical in each of the two exemplaryembodiment described above.

Referring now to FIG. 5, a fan motor, such as motor 50 was tested forefficiency and measured temperature. As shown in FIG. 5, at column 502,the heat distribution with a conventional cooling construction was veryuneven, with an 11.3° C. differential between front coils 27 and rearcoils 26.

In FIG. 6, motor 100 was tested where the only difference between motor100 and motor 10 was the improved cooling provided by motor housings102, 103, front cover 104 and rear cover 101. As shown in FIG. 6, atcolumn 602, the temperatures of the front and rear coil windings 114 and112 were the same and were significantly lower than the temperaturesrecorded for motor 10 by greater than 19° C. for the rear coils and bygreater than 30° C. for the front coils. As shown in FIG. 7, it iscontemplated that this improved motor assembly 300 may be used in anoscillating fan 700, for example.

Although the invention has been described with reference to exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed to include other variants and embodiments of theinvention, which may be made by those skilled in the art withoutdeparting from the true spirit and scope of the present invention.

1. An electric fan motor comprising: a first motor housing having atleast one inlet opening disposed on a surface of the first motorhousing; a second motor housing having at least one outlet openingdisposed on a surface of the second motor housing; and a statorcomprising: i) a plurality of laminations formed in a stack andsubstantially disposed within at least one of the first motor housingand the second motor housing, the stack having a plurality of passagesformed therethrough, ii) windings passing within at least a portion ofsaid plurality of passages, iii) a first portion of the windingsdisposed on a first side of the stack and substantially within the firstmotor housing, and, iv) a second portion of the windings disposed on asecond side of the stack and substantially within the second motorhousing, wherein the at least one inlet opening is in fluidcommunication with the at least one outlet opening and air flows i) intothe at least one inlet opening, ii) over the first portion of windings,substantially all of an exterior portion of the plurality oflaminations, and the second portion of windings, and iii) out the atleast one outlet opening.
 2. An electric motor according to claim 1further comprising, a motor cover substantially enclosing the first andsecond motor housings therein, the motor cover including: i) a firstcover coupled to the second motor housing, the first cover having atleast one opening in a surface thereof, the at least one openingadjacent and in fluid communication with the at least one opening in thesecond motor housing, and ii) a second cover coupled to the first coverand substantially surrounding the first and second motor housings, thesecond cover having at least one opening in a surface thereof, the atleast one opening adjacent and in fluid communication with the at leastone opening in the first motor housing.
 3. An electric motor accordingto claim 2 wherein the first and second covers are formed from at leastone of a metal and a polymer.
 4. An electric motor according to claim 2,wherein the second cover is coupled to a portion of the first motorhousing.
 5. An electric motor according to claim 2, further comprisingmeans for sealing the first cover to the second cover.
 6. An electricmotor according to claim 1 further comprising, a motor coversubstantially enclosing the first and second motor housings therein, themotor cover including: i) a first cover coupled to the second motorhousing and substantially surrounding the first and second motorhousings, the first cover having at least one opening in a surfacethereof, the at least one opening adjacent and in fluid communicationwith the at least one opening in the second motor housing, and ii) asecond cover coupled to the first cover, the second cover having atleast one opening in a surface thereof, the at least one openingadjacent and in fluid communication with the at least one opening in thefirst motor housing.
 7. An electric motor according to claim 1, whereinthe first and second motor housings are formed from a metal.
 8. Anelectric motor according to claim 1, wherein the stator is substantiallysquare.
 9. An electric motor according to claim 1, wherein the stator issubstantially round.
 10. An electric motor according to claim 1, whereinan end portion of the stator is coupled to at least one of the first andsecond motor housings.
 11. An electric motor according to claim 1,wherein the at least one opening in the first motor housing and the atleast one opening in the second motor housing are in respective planesthat are substantially parallel to one another.
 12. An electric motoraccording to claim 1, further comprising: a rotor at least partiallydisposed adjacent the stator, a shaft coupled to the rotor and extendingthrough the second motor housing such that an end portion of the shaftis positioned external the second motor housing; and a fan blade coupledto the end portion of the shaft and adjacent the at least one outletopening.
 13. An oscillating fan incorporating the electric motoraccording to claim
 1. 14. An electric fan motor comprising: a firstmotor housing comprising: i) a first wall defining a first interiorspace, ii) at least one opening disposed on a surface of the first motorhousing, and iii) a mating surface; a second motor housing comprising:i) a second wall defining a second interior space, ii) at least oneopening disposed on a surface of the second motor housing, and iii) amating surface; and a stator comprising: i) a plurality of laminationscoupled to a portion of the mating surface of the first motor housingand a second surface coupled to the mating surface of the second motorhousing, ii) a first portion of windings disposed within only the firstinterior space, and iii) a second portion of windings disposed withinonly the second interior space, wherein the air flows i) into the atleast one opening in the first motor housing, ii) over the first portionof windings, substantially all of an exterior portion of the pluralityof stator laminations, and the second portion of windings, and iii) outthe at least one opening in the second motor housing.
 15. An electricmotor comprising: a first motor housing comprising: i) a first walldefining a first interior space, and ii) at least one opening disposedon a surface of the first motor housing; a second motor housingcomprising: i) a second wall defining a second interior space, and ii)at least one opening disposed on a surface of the second motor housing;and a stator comprising i) a plurality of laminations, ii) a firstportion of windings and iii) a second portion of windings, the pluralityof laminations disposed substantially within a space defined by acombination of the first Interior space and the second interior space,wherein air flows i) into the at least one opening in the first housing,ii) over the first portion of windings, substantially all of an exteriorportion of the plurality of stator laminations, and the second portionof windings, and iii) out the at least one opening in the secondhousing.
 16. An oscillating fan incorporating the electric motoraccording to claim
 15. 17. An electric fan motor comprising: a firstmotor housing having at least one inlet opening disposed on a surface ofthe first motor housing; a second motor housing having at least oneoutlet opening disposed on a surface of the second motor housing; and astator comprising: i) a plurality of laminations formed in a stack andsubstantially disposed within at least one of the first motor housingand the second motor housing, the stack having a plurality of passagesformed therethrough, ii) windings passing within at least a portion ofsaid plurality of passages, iii) a first portion of the windingsdisposed on a first side of the stack and adjacent an end wail of thefirst motor housing, and, iv) a second portion of the windings disposedon a second side of the stack and adjacent an end wall of the secondmotor housing, wherein the at least one inlet opening is in fluidcommunication with the at least one outlet opening and air flows i) intothe at least one inlet opening, ii) over the first portion of windings,substantially all of an exterior portion of the plurality oflaminations, and the second portion of windings, and iii) out the atleast one outlet opening.
 18. An electric fan motor comprising: a firstmotor housing comprising: i) a first wall defining a first interiorspace, ii) at least one opening disposed on a surface of the first motorhousing, and iii) a mating surface; a second motor housing comprising:i) a second wall defining a second interior space, ii) at least oneopening disposed on a surface of the second motor housing, and iii) amating surface; and a stator comprising: i) a plurality of laminationscoupled to the first motor housing and the second motor housing, and ii)a first portion of windings and a second portion of windings disposedsubstantially within at least one of the first and second motorhousings, wherein the air flows i) into the at least one opening in thefirst motor housing, ii) over the first portion of windings,substantially all of an exterior portion of the plurality of statorlaminations, and the second portion of windings, and iii) out the atleast one opening in the second motor housing.